Hydrostatic continuously variable transmission

ABSTRACT

A hydrostatic continuously variable transmission is configured by connecting a swash plate type plunger hydraulic pump P and a swash plate type plunger hydraulic motor via a hydraulic closed circuit. A continuous shift control is executed by variably controlling an inclined angle of the swash plate of the hydraulic motor. A valve spool movably arranged in a spool hole axially extends in a shaft that supports the hydraulic pump and the hydraulic motor and is configured by coupling a first spool member provided with a guide land fitted in a guide member and a second spool member provided with a central land and a left land and provided with a valve that connects and cuts off a clutch oil passage on the high pressure side and a clutch oil passage on the low pressure side according to axial movement by a coupling pin.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 USC 119 to JapanesePatent Application No. 2007-095034 filed on Mar. 30, 2007 the entirecontents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydrostatic continuously variabletransmission configured by connecting a hydraulic pump and a hydraulicmotor via a hydraulic closed circuit and configured to enable variablycontrolling of the capacity of at least either of the hydraulic pump orthe hydraulic motor, shifting the input revolution speed of thehydraulic pump and acquiring the output revolution speed of thehydraulic motor.

2. Description of Background Art

Various configurations of a hydrostatic continuously variabletransmission are known. For example, hydrostatic continuously variabletransmissions have been proposed and disclosed in JP-A No. H6-42446; JPPatent No. 2920772; JP-A No. H9-100909 and JP-A No. 2005-256979 by theapplicants. These hydrostatic continuously variable transmissionsdisclosed in these patents and applications are each provided with aswash plate type plunger pump, a swash plate type plunger motor and ahydraulic closed circuit that connects a discharge port and a suctionport of the swash plate type plunger pump to a suction port and adischarge port of the swash plate type plunger motor. The hydrostaticcontinuously variable transmission is configured so that a pump swashplate is driven by an engine, a pump cylinder and a motor cylinder areconnected and are arranged on an output shaft, the rotation of a motorswash plate is regulated, and an angle of the motor swash plate can bevariably adjusted.

A hydrostatic continuously variable transmission configured as describedabove is known. A clutch valve is provided that connects and cuts off anoil passage on the high pressure side and an oil passage on the lowpressure side respectively forming the hydraulic closed circuit. Aquantity in which a rotational driving force from the hydraulic pump istransmitted to the hydraulic motor is controlled. A clutch control forcutting off the rotational transmission is executed. For example, inJP-A No. 2005-256979, an automatic clutch using such a clutch valve isdisclosed. This clutch valve is provided with a valve spool movablyarranged in a spool hole axially extending in the supporting shaft thatrotatably supports the hydraulic pump and the hydraulic motor, andconnects and cuts off the oil passage on the high pressure side and theoil passage on the low pressure side by axially moving the valve spool.The clutch valve is provided with a spring (energizing means) thatenergizes the valve spool in a direction of disengagement and acentrifugal governor that generates a force corresponding to inputrevolution speed. The clutch valve is opened and closed according to abalance among the energizing force by the spring, a governor force and aload depending upon internal pressure high pressure), and executescontrol for connecting and cutting off the oil passage on the highpressure side and the oil passage on the low pressure side.

In the above-mentioned clutch valve, the valve spool requires a partthat receives an energizing force by the spring and governor force, apart that guides to enable an axial smooth movement in the spool holeand a part that connects and cuts off the oil passage on the highpressure side and the oil passage on the low pressure side according tothe axial movement. Thus, the valve spool is formed in an axially longshape. In this case, as high precision is required for the peripheraldimension of a guide part fitted into a guide hole formed in thesupporting shaft and guided to be axially moved in the spool hole andthe peripheral dimension of a valve part fitted to a part in which theoil passage on the high pressure side and the oil passage on the lowpressure side are open in the spool hole for connecting and cutting offthe oil passage on the high pressure side and the oil passage on the lowpressure side according to the axial movement, the above-mentionedclutch valve has a problem in that the manufacture of the valve spool isdifficult and a great deal of manufacturing cost is required. Further, aproblem exists wherein the precision is not met. Thus, the operationperformance may be deteriorated.

SUMMARY AND OBJECTS OF THE INVENTION

The invention is made in view of such problems. It is an object of anembodiment of the present invention to provide a hydrostaticcontinuously variable transmission where the manufacture of a valvespool forming a clutch valve is simple and the manufacturing cost can bereduced.

The hydrostatic continuously variable transmission according to anembodiment of the present invention is configured by connecting ahydraulic pump and a hydraulic motor via a hydraulic closed circuitwherein the capacity of at least either of the hydraulic pump or thehydraulic motor is variably controlled. The input revolution speed ofthe hydraulic pump is shifted and the output revolution speed of thehydraulic motor is acquired. The hydrostatic continuously variabletransmission according to an embodiment of the present invention isprovided with the valve spool movably arranged in a spool hole axiallyextending in a supporting shaft that rotatably supports the hydraulicpump and the hydraulic motor. A clutch oil passage on the high pressureside is connected to an oil passage on the high pressure side formingthe hydraulic closed circuit and is open to the spool hole. A clutch oilpassage on the low pressure side is connected to an oil passage on thelow pressure side forming the hydraulic closed circuit and is open tothe spool hole. The valve spool is provided with a guide part fittedinto a guide hole formed in the supporting shaft and guided so that theguide part is axially moved in the spool hole with a valve part fittedto a part in which the clutch oil passage on the high pressure side andthe clutch oil passage on the low pressure side in the spool hole areopen for connecting and cutting off the clutch oil passage on the highpressure side and the clutch oil passage on the low pressure sideaccording to the axial movement. Further, the valve spool is formed bycoupling a first spool member provided with a part in which the guidepart is formed and a second spool member provided with a part in whichthe valve part is formed.

It is desirable that the first spool member and the second spool membercoaxially extend and are mutually rockably coupled by a coupling pinextending in a direction perpendicular to the axis.

It is desirable that in the hydrostatic continuously variabletransmission, a high dimensional precision is required for two or lessperipheral parts of the first spool member to fit the peripheral partsto the guide hole in the first spool member. A high dimensionalprecision is required for two or less peripheral parts of the secondspool member to fit the peripheral parts to the spool hole in the secondspool member.

According to the hydrostatic continuously variable transmissionconfigured as described above according to an embodiment of the presentinvention, as the valve spool is formed by coupling the first spoolmember is provided with the part in which the guide part is formed andthe second spool member is provided with the part in which the valvepart is formed, the valve spool is formed only by coupling the first andsecond spool members after they are separately manufactured. Therefore,the manufacture is facilitated, the manufacturing cost can be reduced,and dimensional precision can be enhanced. More specifically, as it isfor only the guide part in the first spool member that high dimensionalprecision is required, the manufacture is simple and as it is also foronly the valve part in the second spool member that high dimensionalprecision is required, the manufacture is simple.

When the first and second spool members coaxially extend and aremutually rockably coupled by a coupling pin extended in a directionperpendicular to the axis, their coupled structure is simple.

When a high dimensional precision is required for respective two or lessperipheral parts in the first and second spool members, the highdimensional precision is secured. In addition, the manufacture can befacilitated.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1 is a sectional view showing the configuration of a hydrostaticcontinuously variable transmission according to the invention;

FIG. 2 is an outside drawing showing a motorcycle provided with thehydrostatic continuously variable transmission;

FIG. 3 is a schematic drawing showing the power transmission pathconfiguration of a power unit provided with the hydrostatic continuouslyvariable transmission;

FIG. 4 is a sectional view showing the configuration of the hydrostaticcontinuously variable transmission;

FIG. 5 is a sectional view enlarged to show the configuration of a partof the hydrostatic continuously variable transmission;

FIG. 6 is a sectional view enlarged to show the configuration of thepart of the hydrostatic continuously variable transmission.

FIG. 7 is a front view and a sectional view showing a cotter used forpositioning a rotor in the hydrostatic continuously variabletransmission;

FIG. 8 is a front view and a sectional view showing a retainer ring usedfor positioning the rotor in the hydrostatic continuously variabletransmission;

FIG. 9 is a front view and a sectional view showing a snap ring used forpositioning the rotor in the hydrostatic continuously variabletransmission;

FIG. 10 is a sectional view showing a motor servo mechanism in thehydrostatic continuously variable transmission;

FIG. 11 is a sectional view showing the structure of a hydraulic pumpand a clutch in the hydrostatic continuously variable transmission;

FIG. 12 is a sectional view showing the structure of a transmissionoutput shaft and the output rotor in the hydrostatic continuouslyvariable transmission;

FIG. 13 is a sectional view showing the structure of the transmissionoutput shaft and the output rotor in the hydrostatic continuouslyvariable transmission;

FIG. 14 is a sectional view showing the structure of the transmissionoutput shaft and the output rotor in the hydrostatic continuouslyvariable transmission;

FIG. 15 is a sectional view showing the structure of a lock-up mechanismin the hydrostatic continuously variable transmission;

FIG. 16 is a sectional view showing the structure when the lock-upmechanism is located in a normal position in a condition viewed along aline Y-Y shown in FIG. 15;

FIG. 17 is a sectional view showing the structure when the lock-upmechanism is located in a lock-up position in a condition viewed alongthe line Y-Y shown in FIG. 15;

FIG. 18 is a hydraulic circuit diagram showing the oil passageconfiguration of the hydrostatic continuously variable transmission;

FIG. 19( a) is a partial sectional view showing the configuration of avalve spool forming the clutch of the hydrostatic continuously variabletransmission, FIGS. 19( b) and 19(c) are view showing the retainingring; and

FIG. 20 is a sectional view showing the configuration of thecircumference of a motor swash plate in a condition close to the gearratio of 1.0 in the hydrostatic continuously variable transmission.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, a preferred embodiment of the invention willbe described below. FIG. 2 illustrates the whole appearance of amotorcycle that is provided with a hydrostatic continuously variabletransmission according to the invention. FIG. 2 shows a condition inwhich a side cover of the motorcycle is partially removed and itsinternal structure is exposed. This motorcycle 100 is provided with amain frame 110, a front fork 120 turnably attached to a front end of themain frame 110 with a diagonally vertically extended axis in the center,a front wheel 101 rotatably attached to a lower end of the front fork120, a swing arm 130 vertically rockably fastened to the rear of themain frame 110 with a horizontally extended fastening shaft 130 a in thecenter and a rear wheel 102 rotatably attached to a rear end of theswing arm 130.

A fuel tank 111 is provided together with a seat 112 for an occupant tosit, a main stand 113 a and a substand 113 b. A headlight 114 isprovided that radiates light ahead during night driving. In addition, aradiator 115 is provided for cooling engine cooling water, a power unitPU is provided for generating rotational driving force for driving therear wheel 102 and other parts are attached to the main frame 110. Ahandlebar (a steering handlebar) 121 is provided for the occupant tooperate so as to steer the motorcycle, a rear view mirror 122 isprovided for acquiring a back field of view and other parts are attachedto the front fork 120. A drive shaft for transmitting the rotationaldriving force generated by the power unit PU to the rear wheel isprovided in the swing arm 130 as described later.

In the motorcycle 100 configured as described above, the hydrostaticcontinuously variable transmission CVT is used for the power unit PU andthe power unit PU will be described below. First, FIG. 3 shows theschematic configuration of the power unit PU and the power unit PU isprovided with an engine E that generates rotational driving force, thehydrostatic continuously variable transmission CVT that continuouslyshifts output rotation and a transmission gear train GT that switches arotational direction output from the hydrostatic continuously variabletransmission CVT and transmits the output rotation.

As shown in FIG. 2, the engine E is a V-type engine provided with aV-type bank with cylinders 1 that extend diagonally upwardly in alongitudinal direction in a V type. The engine E is configured byarranging a piston 2 in each cylinder 1 provided with intake and exhaustvalves 1 a, 1 b in each head. In the engine E, the intake valve 1 a andthe exhaust valve 1 b are opened and closed at predetermined times,air-fuel mixture is combusted in the cylinder chamber for reciprocatingthe piston 2, the reciprocation of the piston 2 is transmitted to acrankcase 3 a via a connecting rod 2 a, and a crankshaft 3 is rotated.An input driving gear 4 provided with a damper 4 a is attached to an endof the crankshaft 3 and the rotational driving force of the crankshaft 3is transmitted to the input driving gear 4.

A driving sprocket 8 a is attached to the crankshaft 3 and transmits therotational driving force to a driven sprocket 8 c attached to pumpdriving shafts 9 a, 9 b via a chain 8 b. An oil pump OP and a water pumpWP are arranged on the pump driving shafts 9 a, 9 b as shown in FIG. 3and are driven by the engine E. Hydraulic fluid discharged from the oilpump OP is supplied as replenishment oil and lubricating oil of thehydrostatic continuously variable transmission CVT as described later.As shown in FIG. 2, the hydraulic fluid is cooled by an oil cooler 116arranged in a rear lower part of the power unit PU, and is filtered byan oil filter 117. Cooling water discharged from the water pump WP isused for cooling the engine E, however, the cooling water thetemperature of which rises because of the engine E is cooled by theradiator 115.

The hydrostatic continuously variable transmission CVT is also providedwith a swash plate type plunger hydraulic pump P and a swash plate typeplunger hydraulic motor M. An input driven gear 5 connected to a pumpcasing that forms the swash plate type plunger hydraulic pump P and isengaged with the input driving gear 4. The rotational driving force ofthe engine E is transmitted to the input driven gear 5, and the pumpcasing is rotated. The hydraulic pump P is a fixed capacity type with anangle of a swash plate of which that is fixed. The hydraulic motor M isa variable capacity type with an angle of a swash plate that isvariable. The hydraulic motor is provided with a motor servomechanism SVfor variably adjusting the angle of the swash plate. Though the detailsof the hydrostatic continuously variable transmission CVT are describedlater, the output rotation variably shifted by the hydrostaticcontinuously variable transmission CVT is output to a transmissionoutput shaft 6.

The transmission gear train GT is connected to the transmission outputshaft 6, and switching between a forward motion and neutral,deceleration and others are applied to the rotation of the transmissionoutput shaft 6 by the transmission gear train GT. The transmission geartrain GT is provided with a counter shaft 10 and a first output drivingshaft 15 respectively extending in parallel with the transmission outputshaft 6. The transmission gear train GT is also provided with a firstgear 11 connected to the transmission output shaft 6, a second gear 12arranged so that the second gear can be axially slid on the countershaft 10 and is rotated integrally with the counter shaft 10, a thirdgear 13 connected to the counter shaft 10 and a fourth gear 14ordinarily engaged with the third gear 13 and connected to the firstoutput driving shaft 15. The second gear 12 is axially slid on thecounter shaft 10 according to the operation for a change by the rider,is engaged with the first gear 11 to be a forward motion, and is alsoseparated from the first gear 11 to be neutral.

An output driving bevel gear 15 a is attached to an end of the firstoutput driving shaft 15 and the rotational driving force is transmittedfrom an output driven bevel gear 16 a engaged with the output drivingbevel gear 15 a to a second output driving shaft 16. The second outputdriving shaft 16 is connected to the drive shaft 18 via a universaljoint 17. The drive shaft 18 is connected to the rear wheel 102 throughthe inside of the swing arm 130 as described above with the rotationaldriving force being transmitted to the rear wheel 102 for driving therear wheel. The universal joint 18 is located coaxially with thefastening shaft 130 a for fastening the swing arm 130 to the main frame110.

Referring to FIGS. 1 and 4 to 6, the hydrostatic continuously variabletransmission CVT will be described. The hydrostatic continuouslyvariable transmission CVT is provided with the swash plate type plungerhydraulic pump P and the swash plate type plunger hydraulic motor M andthe transmission output shaft 6 extends with the output shaft piercingits center. The transmission output shaft 6 is rotatably supported by atransmission housing IISG via ball bearings 7 a, 7 b, 7 c.

The hydraulic pump P is configured by the pump casing 20 arranged on thetransmission output shaft 6 coaxially and relatively rotatably with thetransmission output shaft 6. A pump swash plate 21 is arranged insidethe pump casing 20 with the pump swash plate tilted by a predeterminedangle with a rotational central axis of the pump casing 20. A pumpcylinder 22 is arranged opposite to the pump swash plate 21 with pluralpump plungers 23 slidably arranged in each pump plunger hole 22 aaxially extending in an annular arrangement encircling a central axis ofthe pump cylinder in the pump cylinder 22. The pump casing 20 isrotatably supported by bearings 7 b and 22 c on the transmission outputshaft 6 and on the pump cylinder 22 and is rotatably supported by thebearing 7 a on the transmission housing HSG. The pump swash plate 21 isrotatably arranged with its axis tilted by bearings 21 a, 21 b by apredetermined angle with the pump casing 20 in the center. Morespecifically, the pump cylinder 22 is supported by the bearing 22 ccoaxially and relatively rotatably with the pump casing 20.

The input driven gear 5 is fastened to the periphery of the pump casing20 by a bolt 5 a. An outer end of the pump plunger 23 projectsoutwardly, is touched and fitted to a swash surface 21 a of the pumpswash plate 21, and its inner end located in the pump plunger hole 22 aforms a pump oil chamber 23 a in the pump plunger hole 22 a opposite toa valve body 51 of a distributing valve 50 described later. A pumpopening 22 b that acts as a pump discharge port and a pump inlet isformed at the end of the pump plunger hole 22 a. When the input drivengear 5 is driven as described above, the pump casing 20 is rotated, thepump swash plate 21 arranged inside the pump casing is rocked by therotation of the pump casing 20, the pump plunger 23 is reciprocated inthe pump plunger hole 22 a according to the rocking of the swash platesurface 21 a, and hydraulic fluid inside the pump oil chamber 23 a isdischarged and is sucked.

A pump eccentric member 20 a is connected to a right end in the drawingsof the pump casing 20 by a bolt 5 b. An inside face 20 b of the pumpeccentric member 20 a is formed in the shape of a cylinder eccentricwith a rotational axis of the pump casing 20. The pump eccentric member20 a is provided with the inside face 20 b eccentric as described aboveand is formed separately from the pump casing 20. Thus, the assembly issimple to manufacture.

The hydraulic motor M is configured by a motor casing 30 (formed byplural casings 30 a, 30 b) connected, fixed and held to/by thetransmission housing HSG. A motor rocking member 35 is slidablysupported by a supporting cylindrical surface 30 c formed on an insideface of the motor casing 30 (the casing 30 b) and is rockably supportedwith the center O of the rocking that extends in a direction (adirection perpendicular to a paper face) of a right angle with a centralaxis of the transmission output shaft 6 in the center. A motor swashplate 31 is rotatably supported by bearings 31 a, 31 b inside the motorrocking member 35 with a motor cylinder 32 being opposite to the motorswash plate 31. A plurality of motor plungers 33 are slidably arrangedin each motor plunger hole 32 a axially pierced in an annulararrangement encircling a central axis of the motor cylinder in the motorcylinder 32. The motor cylinder 32 is rotatably supported by the motorcasing 30 via a bearing 32 c on the periphery of the motor cylinder.

In the hydraulic motor M, a lock-up mechanism 90 (see FIGS. 15 to 17) isprovided to a left end in the drawings of the motor casing 30 and amotor eccentric member 91 forming the lock-up mechanism 90 is slidablytouched to an end of the motor casing 30. The lock-up mechanism 90 willbe described later, however, it is rocked between a lock-up position inwhich a cylindrical inside face 91 a formed on the motor eccentricmember 91 is located coaxially with the motor cylinder 32 and a normalposition in which the cylindrical inside face is located in an eccentricposition with a rotational axis of the motor cylinder 32.

An outer end of the motor plunger 33 projects outwardly and is touchedto a face 31 a of the motor swash plate 31. An inner end located in theplunger hole 32 a is opposite to the valve body 51, and forms a motoroil chamber 33 a in the motor plunger hole 32 a. A motor opening 32 b,that acts as a motor discharge port and a motor inlet, is formed at theend of the motor plunger hole 32 a. An arm part 35 a formed byprotruding an end of the motor rocking member 35 on the side of anoutside diameter projects outwardly in a radial direction and is coupledto the motor servomechanism SV. Control for moving the arm part 35 alaterally in FIG. 1 and others is executed by the motor servomechanismSV and control for rocking the motor rocking member 35 with the center Oof rocking in the center is executed. When the motor rocking member 35is rocked as described above, the motor swash plate 31 rotatablysupported inside the motor rocking member is also rocked together, andan angle of the swash plate varies.

The distributing valve 50 is arranged between the pump cylinder 22 andthe motor cylinder 32. FIGS. 5 and 6 show the part with the partenlarged, the valve body 51 of the distributing valve 50 is held betweenthe pump cylinder 22 and the motor cylinder 32, is integrated with themby brazing, and the motor cylinder 32 is connected to the transmissionoutput shaft 6 via a spline. Therefore, the pump cylinder 22, thedistributing valve 50, the motor cylinder 32 and the transmission outputshaft 6 are integrally rotated.

The pump cylinder 22, the distributing valve 50 (its valve body 51) andthe motor cylinder 32 respectively integrated as described above arecalled an output rotor and are configuration for positioning andattaching the output rotor in an axial predetermined position on thetransmission output shaft 6 will be described below. A regulating part 6f projecting in the shape of a flange on the peripheral side of thetransmission output shaft 6 is formed for the positioning, a left endface of the pump cylinder 22 is touched to the regulating part 6 f, andto the left positioning is performed. In the meantime, the to the rightpositioning of the output rotor is performed by a fitting member 80attached to the transmission output shaft 6 opposite to a right end faceof the motor cylinder 32.

As shown in FIGS. 12 to 14 in detail, a first fitting groove 6 g and asecond fitting groove 6 h respectively annular are formed on thetransmission output shaft 6 so as to attach the fitting member 80.Inside faces 81 a of a pair of cotters 81 formed by dividing in asemicircle as shown in FIG. 7 are fitted into the first fitting groove 6g. A retainer ring 82 shown in FIG. 8 is attached on the cotters, a sideplate 82 b of the retainer ring 82 is touched to the sides of thecotters 81, a peripheral plate 82 a covers outside faces 81 b of thecotters 81, and the retainer ring holds the cotters 81 in thiscondition. Further, a snap ring 83 shown in FIG. 9 is fitted into thesecond fitting groove 6 h and holds the retainer ring 82 in thiscondition. As a result, the right end face of the motor cylinder 32 istouched to the fitting member 80 and right positioning is performed. Asknown from the above-mentioned configuration, the output rotor ispositioned on the transmission output shaft 6 between the regulatingpart 6 f and the fitting member 80.

The distributing valve 50 will be described as illustrated in FIGS. 5and 6. A plurality of pump-side spool holes 51 a and a plurality ofmotor-side spool holes 51 b respectively extend in a radial directionand are formed at an equal interval in a circumferential direction areformed in two rows in the valve body 51 forming the distributing valve50. A pump-side spool 53 is slidably arranged in the pump-side spoolhole 51 a and a motor-side spool 55 is slidably arranged in themotor-side spool hole 51 b.

The pump-side spool hole 51 a is formed corresponding to the pumpplunger hole 22 a and the plurality of pump-side communicating passages51 c each of which connects the corresponding pump opening 22 b (thecorresponding pump oil chamber 23 a) and the corresponding pump-sidespool hole 51 a are formed in the valve body 51. The motor-side spoolhole 51 b is formed corresponding to the motor plunger hole 32 a and theplurality of motor-side communicating passages 51 d each of whichconnects the corresponding motor opening 32 b (the corresponding motoroil chamber 33 a) and the corresponding motor-side spool hole 51 b areformed in the valve body 51.

In the distributing valve 50, a pump-side cam ring 52 is furtherarranged in a position encircling a peripheral end of the pump-sidespool 52 and a motor-side cam ring 54 is further arranged in a positionencircling a peripheral end of the motor-side spool 55. The pump-sidecam ring 52 is attached to the inside face 20 b made eccentric from therotational central axis of the pump casing 20 on the inner surface ofthe pump eccentric member 20 a connected to an end of the pump casing 20by the bolt 5 b and is rotatably supported by the pump casing 20. Themotor-side cam ring 54 is attached on an inside face 91 a of a motoreccentric member 91 slidably located at the end of the motor casing 30.A peripheral end of the pump-side spool 53 is relatively rotatablyfitted to an inside face of the pump-side cam ring 52 and a peripheralend of the motor-side spool 55 is relatively rotatably fitted to aninside face of the motor-side cam ring 54.

An inside passage 56 is formed between an inside face of the valve body51 and the periphery of the transmission output shaft 6 and inside endsof the pump-side spool hole 51 a and the motor-side spool hole 51 bcommunicate with the inside passage 56. In addition, an outside passage57 that connects the pump-side spool hole 51 a and the motor-side spoolhole 51 b is formed in the valve body 51.

The action of the distributing valve 50 configured as described abovewill be described. When the driving force of the engine E is transmittedto the input driven gear 5 and the pump casing 20 is rotated, the pumpswash plate 21 is rocked according to the rotation. Therefore, the pumpplunger 23 touched and fitted to the swash surface 21 a of the pumpswash plate 21 is axially reciprocated in the pump plunger hole 22 a bythe rocking of the pump swash plate 21, hydraulic fluid is dischargedfrom the pump oil chamber 23 a via the pump opening 22 b according tothe inside movement of the pump plunger 23, and is sucked in the pumpoil chamber 23 a through the pump opening 22 b according to the outsidemovement.

At this time, the pump-side cam ring 52 attached to the inside face 20 bof the pump eccentric member 20 a connected to the end of the pumpcasing 20 is rotated together with the pump casing 20. However, as thepump-side cam ring 52 is attached with the pump-side cam ring eccentricwith the rotational center of the pump casing 20, the pump-side spool 53is reciprocated in the radial direction in the pump-side spool hole 51 aaccording to the rotation of the pump-side cam ring 52. When thepump-side spool 53 is reciprocated and is moved on the side of an insidediameter from a condition shown in FIGS. 5 and 6 as described above, thepump-side communicating passage 51 c and the outside passage 57communicate via a spool groove 53 a. When the pump-side spool 53 ismoved on the side of an outside diameter from the condition shown inFIGS. 5 and 6, the pump-side communicating passage 51 c and the insidepassage 56 communicate.

While the swash plate 21 is rocked according to the rotation of the pumpcasing 20 and the pump plunger 23 is reciprocated between a position(called a bottom dead center) in which the pump plunger is pushed on theoutermost side and a position (called a top dead center) in which thepump plunger is pushed on the innermost side, the pump-side cam ring 52reciprocates the pump-side spool 53 in the radial direction. As aresult, when the pump plunger 23 is moved from the bottom dead center tothe top dead center according to the rotation of the pump casing 20 andthe hydraulic fluid in the pump oil chamber 23 a is discharged via thepump opening 22 b, the hydraulic fluid is delivered into the outsidepassage 57 through the pump-side communicating passage 51 c. In themeantime, when the pump plunger 23 is moved from the top dead center tothe bottom dead center according to the rotation of the pump casing 20,hydraulic fluid in the inside passage 56 is sucked in the pump oilchamber 23 a through the pump-side communicating passage 51 c and thepump opening 22 b. As known from this, when the pump casing 20 isrotated, hydraulic fluid discharged from the hydraulic pump P issupplied to the outside passage 57 and the hydraulic fluid is sucked inthe hydraulic pump P from the inside passage 56.

In the meantime, as the motor-side cam ring 54 attached on the insideface 91 a of the motor eccentric member 91 slidably located at the endof the motor casing 30 is eccentric with the rotational center of themotor cylinder 32 (the output rotor and the transmission output shaft 6)when the motor eccentric member 91 is located in a normal position, themotor-side spool 55 is reciprocated in the radial direction in themotor-side spool hole 51 b according to the rotation of the motorcylinder 32. When the motor-side spool 55 is reciprocated as describedabove and is moved on the side of the inside diameter from the conditionshown in FIGS. 5 and 6, the motor-side communicating passage 51 d andthe outside passage 57 communicate via a spool groove 55 a. When themotor-side spool 55 is moved on the side of the outside diameter fromthe condition shown in FIGS. 5 and 6, the motor-side communicatingpassage 51 d and the inside passage 56 communicate. A situation whereinthe motor eccentric member 91 is located in a lock-up position will bedescribed later and the situation wherein the motor eccentric member islocated in the normal position is described above.

As described above, hydraulic fluid discharged from the hydraulic pump Pis delivered into the outside passage 57, is supplied to the motor oilchamber 33 a from the motor-side communicating passage 51 d via themotor opening 32 b, and the motor plunger 33 is thrusted axiallyoutward. As described above, the motor plunger is configured so that anoutside end of the motor plunger 33 to which the axial outward pressureis applied is slid from the top dead center to the bottom dead center onthe motor swash plate 31 in a condition shown in FIG. 1 in which themotor rocking member 35 is rocked, and the motor cylinder 32 is rotatedso that the motor plunger 33 is moved from the top dead center to thebottom dead center along the motor swash plate 31 by the axial outwardthrust.

To enable such rotation, while the motor plunger 33 is reciprocatedbetween the position in which the motor plunger is pushed on theoutermost side (the bottom dead center) and the position in which themotor plunger is pushed on the innermost side (the top dead center)according to the rotation of the motor cylinder 32, the motor-side camring 54 reciprocates the motor-side spool 55 in the radial direction.When the motor cylinder 32 is rotated as described above, the motorplunger 33 is pushed and moved from the bottom dead center to the topdead center, that is, inward along the motor swash plate 31 according tothe rotation and hydraulic fluid in the motor oil chamber 33 a isdelivered into the inside passage 56 from the motor opening 32 b via themotor-side communicating passage 51 d. The hydraulic fluid deliveredinto the inside passage 56 as described above is sucked in the pump oilchamber 23 a through the pump-side communicating passage 51 c and thepump opening 22 b as described above.

As set forth in the above-mentioned description, when the pump casing 20is rotated by the rotational driving force of the engine E, hydraulicfluid is discharged into the outside passage 57 from the hydraulic pumpP, is delivered into the hydraulic motor M, and rotates the motorcylinder 32. The hydraulic fluid that rotates the motor cylinder 32 isdelivered into the inside passage 56 and is sucked in the hydraulic pumpP from the inside passage 56. As described above, a hydraulic closedcircuit connecting the hydraulic pump P and the hydraulic motor M isformed by the distributing valve 50, hydraulic fluid discharged from thehydraulic pump P according to the rotation of the hydraulic pump P isdelivered into the hydraulic motor M via the hydraulic closed circuit,the hydraulic motor is rotated, and further, the hydraulic fluid thatdrives the hydraulic motor M and is discharged is returned to thehydraulic pump P via the hydraulic closed circuit.

In this case, when the hydraulic pump P is driven by the engine E, therotational driving force of the hydraulic motor M is transmitted to thewheels and the vehicle drives, the outside passage 57 is an oil passageon the high pressure side and the inside passage 56 is an oil passage onthe low pressure side. In the meantime, when the driving force of thewheel is transmitted to the hydraulic motor M, the rotational drivingforce of the hydraulic pump P is transmitted to the engine E and enginebrake action is produced as in driving on a descending slope, the insidepassage 56 is turned an oil passage on the high pressure side and theoutside passage 57 is turned an oil passage on the low pressure side. Atthis time, as the pump cylinder 22 and the motor cylinder are connectedto the transmission output shaft 6 and are integrally rotated, the pumpcylinder 22 is also rotated together as described above when the motorcylinder 32 is rotated and relative revolution speed between the pumpcasing 20 and the pump cylinder 22 is reduced. Therefore, the relationbetween the revolution speed Ni of the pump casing 20 and the revolutionspeed No of the transmission output shaft 6 (that is, the revolutionspeed of the pump cylinder 22 and the motor cylinder 32) is as shown inthe following expression (1) in relation to pump capacity Vp and motorcapacity Vm.

(Mathematical Expression 1)

Vp·(Ni−No)=Vm·No  (1)

The motor capacity Vm can be continuously varied by control that themotor rocking member 35 is rocked according to the motor servomechanismSV. That is, when the revolution speed Ni of the pump swash plate 21 isfixed in the expression (1), the revolution speed of the transmissionoutput shaft 6 continuously shifts in control that the motor capacity Vmis continuously varied and as known from this, shift control is executedby rocking the motor rocking member 35 and varying the motor capacity Vmby the motor servomechanism SV.

In a control wherein an oscillation angle of the motor rocking member 35is reduced, the motor capacity Vm decreases. When the pump capacity Vpis fixed and the revolution speed Ni of the pump swash plate 21 is fixedin the relation shown in the expression (1), control that the revolutionspeed of the transmission output shaft 6 is increased so that therevolution speed approaches the revolution speed Ni of the pump swashplate 21, that is, continuous shift control to top speed is executed.When an angle of the motor swash plate is zero, that is, when the motorswash plate is upright, the transmission gear ratio is theoretically thetop gear ratio (Ni=No) to be in a condition wherein the oil pressure islocked, the pump casing 20 is rotated integrally with the pump cylinder22, the motor cylinder 32 and the transmission output shaft 6, andmechanical power transmission is performed.

As described above, the control wherein the motor capacity iscontinuously varied is executed by rocking the motor rocking member 35and variably controlling the angle of the motor swash plate. Mainlyreferring to FIG. 10, the motor servomechanism SV for rocking the motorrocking member 35 as described above will be described below.

The motor servomechanism SV is provided with a ball screw shaft 41located in the vicinity of the arm part 35 a of the motor rocking member35, extending in parallel with the transmission output shaft 6 androtatably supported by the transmission housing HSG via bearings 40 a,40 b and a ball nut 40 screwed on a male screw 41 a formed on theperiphery of the ball screw shaft 41. A ball female screw is formed bymultiple balls held in the shape of a screw according to a gauge on theinside face of the ball nut 40 and is screwed on the male screw 41 a.The ball nut 40 is coupled to the arm part 35 a of the motor rockingmember 35, when the ball screw shaft 41 is rotated, the ball nut 40 ismoved laterally on the ball screw shaft 41, and the motor rocking member35 is rocked.

A swash plate control motor (an electric motor) 47 is attached on theoutside face of the transmission housing HSG to rotate the ball screwshaft 41 as described above. An idle shaft 43 is provided in parallelwith a driving shaft 46 of the swash plate control motor 47 and an idlegear member provided with gears 44 and 45 is rotatably attached on theidle shaft 43. A gear 46 a is formed at the end of the driving shaft 46of the swash plate control motor 47 and is engaged with the gear 45. Inthe meantime, a gear 42 is connected to a shaft part 41 b formed byprotruding a left part of the ball screw shaft 41 to the left and isengaged with the gear 44.

Therefore, when the driving shaft 46 is rotated with the rotation of theswash plate control motor 47 controlled, the rotation is transmitted tothe gear 45, is transmitted from the gear 44 integrally rotated with thegear 45 to the gear 42, and the ball screw shaft 41 is rotated. The ballnut 40 is moved laterally on the shaft 41 according to the rotation ofthe ball screw shaft 41 and control for rocking the motor rocking member35 is executed. As the rotation of the swash plate control motor 47 istransmitted to the ball screw shaft 41 via the gears 46 a, 45, 44, 42 asdescribed above, the transmission ratio can be freely varied by suitablysetting the gear ratio of these gears.

The swash plate control motor 47 is arranged with the swatch controlmotor 47 being exposed outside in the vicinity of the rear side of thebase of the rear cylinder 1 in the V-type engine E as shown in FIG. 2.The cylinder 1 is integrated with the transmission housing HSG and theswash plate control motor 47 is arranged in a space between the rearcylinder 1 and the transmission housing HSG. As the space can beeffectively utilized by arranging the swash plate control motor 47 inthe space between the rear cylinder 1 and the transmission housing HSGas described above and the swash plate control motor is located apartfrom the fastening shaft 130 a of the swing arm 130 shown in FIG. 2, nolimitation for avoiding interference with the swing arm 130 is appliedto the shape of the swing arm. In addition, the swash plate controlmotor 47 can be protected from a splash from the downside of the bodyduring driving from rainwater in a front direction and from dust.Further, the swash plate control motor 47 is arranged with the swatchcontrol motor 47 being biased on the left side from the center in alateral direction of the body as shown in FIG. 10 and is effectivelycooled by efficiently hitting an air flow from the front direction indriving on the swash plate control motor 47.

In the hydrostatic continuously variable transmission CVT configured asdescribed above, when the inside passage 56 and the outside passage 57communicate, no high pressure oil is generated and power transmissionbetween the hydraulic pump P and the hydraulic motor M can be cut off.More specifically, clutch control is enabled by a communication anglecontrol between the inside passage 56 and the outside passage 57. Aclutch CL for the clutch control is provided to the hydrostaticcontinuously variable transmission CVT. As illustrated in FIGS. 11 to14, the clutch CL will be described below.

The clutch CL is configured by a rotor 60 connected to the end of thepump casing 20 by a bolt 60 b, weights 61 (balls or rollers) received inplural receiving grooves 60 a diagonally extend in the radial directionon an inside face of the rotor 60, a disc like pressure receptor 62 isprovided with an arm part 62 a opposite to the receiving groove 60 a. Aspring 63 presses the pressure receptor 62 so that the arm part 62 apresses the weight 61 in the receiving groove 60 a and a valve spool 70is fitted to a fitting part 62 e on one end side of the pressurereceptor 62.

A through hole 60 e having a rotational central axis in the center isformed in the rotor 60, a cylindrical part 62 b of the pressure receptor62 is movably inserted into the through hole 60 c, and the pressurereceptor 62 can be axially moved. Therefore, when the pump casing 20 isstill and the rotor 60 is not rotated, the arm part 62 a presses theweight 61 in the receiving groove 60 a by energizing force applied tothe pressure receptor 62 by the spring 63. At this time, as thereceiving groove 60 a diagonally extends as shown in FIG. 11, the weight61 is pushed inward in the radial direction and the pressure receptor 62is moved to the left as shown in FIGS. 1 and 11.

When the pump casing 20 is rotated and the rotor 60 is rotated from thiscondition, the weight 61 is pushed outward in the radial direction inthe receiving groove 60 a by centrifugal force. When the weight 61 ispushed out in a direction of an outside diameter by centrifugal force asdescribed above, the weight 61 is moved diagonally to the right alongthe receiving groove 60 a, pushes the arm part 62 a to the right and thepressure receptor 62 is moved to the right against the pressure of thespring 63. The quantity in which the pressure receptor 62 is moved tothe right varies according to centrifugal force that acts on the weight61, that is, the revolution speed of the pump casing 20 and when therevolution speed is equal to or exceeds a predetermined revolutionspeed, the pressure receptor is moved to the right to a position shownin FIG. 4. The valve spool 70 fitted to the fitting part 62 c of thepressure receptor 62 is moved axially laterally as described above andis fitted into a spool hole 6 d open to an end of the transmissionoutput shaft 6 and axially extends and is moved axially laterallytogether with the pressure receptor 62.

A governor mechanism that generates an axial governor forcecorresponding to the input revolution speed of the hydraulic pump Pusing a centrifugal force that acts on the weight 61 by the rotation ofthe pump casing 20 is configured by the rotor 60, the weight 61 and thepressure receptor 62.

An inside branched oil passage 6 a branched from the inside passage 56and connected to the spool hole 6 d and outside branched oil passages 6b, 6 c connected from a communicating passage 57 a branched from theoutside passage 57 to the spool hole 6 d are formed in the transmissionoutput shaft 6 in which the spool hole 6 d is formed as shown in FIGS.5, 6 and 11 to 14 in detail. FIGS. 5 and 12 correspond to FIG. 1 andshow a condition wherein the pressure receptor 62 is moved to the leftand the valve spool 70 is moved to the left, in this condition, theinside branched oil passage 6 a and the outside branched oil passage 6 ccommunicate via a right groove 72 of the valve spool 70, and the insidepassage 56 and the outside passage 57 communicate. FIGS. 6 and 14correspond to FIG. 4 and show a condition wherein the pressure receptor62 is moved to the right and the valve spool 70 is moved to the right,in this condition, the inside branched oil passage 6 a and the outsidebranched oil passage 6 c are cut off by a central land 73 of the valvespool 70, and the inside passage 56 and the outside passage 57 are alsocut off. FIG. 13 shows a condition in which the valve spool 70 islocated in an intermediate position.

As described above, as the valve spool 70 is moved to the left when thepump casing 20 is still, the inside branched oil passage 6 a and theoutside branched oil passage 6 c communicate at this time and powertransmission between the hydraulic pump P and the hydraulic motor M iscut off to be in a condition wherein the clutch is disengaged. When thepump casing 20 is driven from this condition, the pressure receptor 62is gradually moved to the right by centrifugal force that acts on theweight 61 according to the number of revolutions and speed of the pumpcasing and the valve spool 70 is also moved to the right together. As aresult the inside branched oil passage 6 a and the outside branched oilpassage 6 c are gradually cut off by the central land 73 of the valvespool 70 and the clutch is gradually engaged.

In the hydrostatic continuously variable transmission CVT according tothis embodiment, when the pump case 20 is rotated by the engine E, thevalve spool 70 is moved to the left to be in the condition that theclutch is disengaged while engine speed is low (in idling) and as theengine speed rises, the clutch is gradually engaged.

An outside diameter d1 of the central land 73 in the valve spool 70 andan outside diameter d2 of a left land 74 are set so that d1<d2.Therefore, when the valve spool 70 is moved to the right to be in thecondition that the clutch is engaged, oil pressure in the outsidepassage 57 that acts in a left groove 75 of the valve spool 70 acts in adirection in which the valve spool 70 is moved to the left. The to theleft thrust corresponds to the magnitude of the oil pressure that actsin the left groove 75 and the difference in the pressure received areadepends upon the difference between the outside diameters d1, d2. Thedifference in the pressure received area is fixed, however, the oilpressure that acts in the left groove 75 is oil pressure in the outsidepassage 57, varies according to the driving force, and the bigger thedriving force is, the higher the oil pressure is. This configuration isequivalent to an oil pressure applying mechanism described in the scopeof claims.

As known from this, clutch engagement control by the movement of thevalve spool 70 is executed according to balance (Fgov=Fp+Fspg) amonggovernor force (Fgov) generated by centrifugal force that acts on theweight 61 corresponding to the number of revolutions and speed of thepump casing 20, energizing force (Fspg) by the spring 63 and thrust (Fp)depending upon the oil pressure that acts in the left groove 75 of thevalve spool 70. Control that the clutch is engaged as the rotation ofthe pump casing 20 increases is executed and control that force in adirection in which the clutch is disengaged is applied as the oilpressure of the outside passage 57 increases (as transmission drivingforce from the hydraulic pump P to the hydraulic motor M increases) isexecuted.

FIG. 13 shows a condition of an intermediate stage when clutchengagement control and clutch disengagement control are executed asdescribed above, that is, a condition of a partial clutch engagement. Inthis condition, a right end 73 a of the central land 73 of the valvespool 70 slightly communicates with the outside branched oil passage 6 bto be in a condition wherein the inside passage 56 and the outsidepassage 57 partially communicate, that is, in the condition of partialclutch engagement. In the condition of partial clutch engagement, theinside passage 56 and the outside passage 57 communicate or are cut offby a slight axial movement of the valve spool 70. However, as the axialmovement of the valve spool 70 is balanced among the governor force(Fgov), the energizing force and the thrust depends upon the oilpressure as described above, the valve spool 70 is operated on the sideon which the clutch is disengaged. When the thrust depends upon the oilpressure rapidly increases by rapid throttle operation, the insidepassage 56 and the outside passage 57 repeat communication and cut off,and it is difficult to stably transmit power.

Therefore, to stabilize clutch performance by preventing the valve spool70 from too sensitively reacting and being moved, a shock absorbingmechanism is provided and referring to FIGS. 1, 4 and 11, the shockabsorbing mechanism will be described below. As shown in these drawings,a variable oil chamber forming groove 76 is provided on the left side ofthe left land 74 of the valve spool 70 and a guide land 71 having asmaller diameter than that of the left land 74 is provided to the leftside of the variable oil chamber forming groove 76. The guide land 71 isfitted in a guide member 77 arranged in a left end of the spool hole 6 dand a variable oil chamber 78 a encircled by the spool hole 6 d, theguide member 77 and the left land 74 is formed on the periphery of thevariable oil chamber forming groove 76.

Further, an oil reservoir forming hole 70 e axially extended in thevalve spool 70 is formed, a right end of the oil reservoir forming hole70 e is open, a modulator valve 150 is arranged, a left end is closed,and an orifice 70 d is formed. As a result, the oil reservoir forminghole 70 e is closed by the modulator valve 150 and an oil reservoir 78 bis formed. A communicating hole 70 c for making the variable oil chamberforming groove 76 and the oil reservoir forming hole 70 e communicate isformed in the valve spool 70, and the variable oil chamber 78 a and theoil reservoir 78 b connect via the communicating hole 70 c.

As described above, the shock absorbing mechanism is configured by thevariable oil chamber 78 a and the oil reservoir 78 b which respectivelyconnect via the communicating hole 70 c and its operation will bedescribed below. When the valve spool 70 is axially moved to the left,the capacity in the variable oil chamber 78 a is reduced because theguide member 77 is fixed in the spool hole 6 d and hydraulic fluid inthe oil chamber is compressed by the left land 74. At this time, as thecapacity in the oil reservoir 78 b cannot be varied, the compressiveforce functions as resistance, the movement of the valve spool 70 isinhibited, and is moderated. In the meantime, when the valve spool 70 isaxially moved to the right, the capacity in the variable oil chamber 78a increases, however, resistance to force in a direction in which thecapacity increases acts by adjusting (reducing) a diameter of thecommunicating hole 70 c, the movement of the valve spool 70 isinhibited, and is moderated.

The left end of the oil reservoir forming hole 70 e is closed, however,the orifice 70 d is formed, as oil flows in the orifice 70 d, themagnitude of the resistance is adjusted by the orifice 70 d. The orifice70 d is open to a coupling part for fining the fitting part 62 c of thepressure receptor 62 and a left end of the valve spool 70 and thecoupling part is lubricated by oil exhausted through the orifice 70 d.

In the shock absorbing mechanism configured as described above, themodulator valve 150 is attached so as to fill hydraulic fluid in thevariable oil chamber 78 a and the oil reservoir 78 b. Referring to FIGS.12 to 14, the modulator valve will be described below. A communicatinghole 70 a that communicates with the modulator valve 150 is formed inthe right groove 72 of the valve spool 70 and hydraulic fluid in theright groove 72 flows into the modulator valve 150 via the communicatinghole 70 a. The modulator valve 150 includes a so-called pressurereducing valves and the hydraulic fluid in the right groove 72 issupplied to the oil reservoir 78 b so that oil pressure in the oilreservoir 78 b is held at a predetermined low pressure set by themodulator valve 150. Therefore, a predetermined low-pressure hydraulicfluid set by the modulator valve 150 is ordinarily filled in thevariable oil chamber 78 a and the oil reservoir 78 b.

As oil in the oil reservoir 78 b is ordinarily exhausted through theorifice 70 d, oil of the exhausted quantity is supplemented via themodulator valve 150. As the supplemented oil is oil in the right groove72 and the right groove 72 communicates with the oil passage 56 on thelow pressure side or the oil passage 57 on the high pressure sideaccording to an engaged/disengaged condition of the clutch, hydraulicfluid in the oil passage 56 on the low pressure side and the oil passage57 on the high pressure side, that is, hydraulic fluid in the hydraulicclosed circuit is used for supplemented oil. Therefore, the hydraulicfluid in the hydraulic closed circuit is ordinarily exhausted by thequantity of supplemented oil, the exhausted hydraulic fluid is replacedwith fresh hydraulic fluid (a hydraulic fluid replacement system will bedescribed later), and the temperature of the hydraulic fluid in theclosed circuit can be prevented from rising.

Further, an exhaust hole 70 b that pierces the valve spool from the oilreservoir 78 b (the oil reservoir forming hole 70 e) to the outside faceof the left land 74 is formed in the valve spool 70 and an exhaust hole6 e that connects from the spool hole 6 d to the outside is formed inthe transmission output shaft 6. As shown in FIG. 13, when the valvespool 70 is located in the partial clutch engagement, both exhaust holes70 b, 6 e communicate via a peripheral groove 70 f of the valve spool70. As a result, in the condition of partial clutch engagement,hydraulic fluid in the oil reservoir 78 b is exhausted outside via bothexhaust holes 70 b, 6 e.

As described above, in the condition of partial clutch engagement, theinside passage 56 and the outside passage 57 partially communicate, ashydraulic fluid flows from the oil passage on the high pressure side tothe oil passage on the low pressure side in the hydraulic closed circuitthrough the partial communicating part the temperature of the hydraulicfluid in the hydraulic closed circuit easily rises. When hydraulic fluidin the oil reservoir 78 b is exhausted outside via both exhaust holes 70b, 6 e in the condition of partial clutch engagement as described above,hydraulic fluid of an exhausted quantity is supplemented via themodulator valve 150. As the supplemented oil is oil in the right groove72 and the right groove 72 communicates with the oil passage 56 on thelow pressure side or the oil passage 57 on the high pressure sideaccording to the engaged/disengaged condition of the clutch, hydraulicfluid in the oil passage 56 on the low pressure side and the oil passage57 on the high pressure side, that is, hydraulic fluid in the hydraulicclosed circuit is used for supplemented oil. Therefore, the hydraulicfluid in the hydraulic closed circuit is ordinarily exhausted by thequantity of supplemented oil, the exhausted oil is replaced with freshhydraulic fluid (the hydraulic fluid replacement system will bedescribed later), and the temperature of the hydraulic fluid in theclosed circuit can be effectively prevented from rising particularly inthe condition of partial clutch engagement.

As the valve spool 70 forming the clutch CL described above is anaxially extended long cylindrical member and high dimensional precisionis required for outside dimensions of the guide land 71 fitted in theguide member 77, the central land 73 and the left land 74, the valvespool is divided into a first spool member 171 and a second spool member172. Referring to FIG. 19, the configuration will be described below.

The first spool member 171 is the cylindrical member provided with afitted part 177 d fitted to the fitting part 62 c of the pressurereceptor 62 at its left end provided with the guide land 71 fitted inthe guide member 77 next to the fitted part. The guide land 71 is fittedin the guide member 77, functions as a part for guiding the axialmovement of the valve spool 70, the fitted part functions as a part forsealing the variable oil chamber 78 a, and its outside dimension isrequired to be finished to have a high precision.

In the first spool member 171, the variable oil chamber forming groove76 is formed on the right side of the guide land 71 and at its rightend, a fitting concave portion 171 a in which a concentric fitting hole171 b is formed that axially extends inward and is open to the right endside. A first coupling hole 171 c extending in a direction perpendicularto the axis is formed in the fitting concave portion 171 a and anannular holding groove 171 d concave in a circumferential direction isformed on the periphery of the first coupling hole 171 c.

In the meantime, in the second spool member 172, a valve part which isprovided with the right groove 72, the central land 73, the left groove75 and the left land 74, which executes communication/cutoff controlbetween the inside branched oil passage 6 a and the outside branched oilpassages 6 b, 6 c and which executes clutch control is formed. In thisvalve part, the central land 73 and the left land 74 function as a valveas described above and their outside dimensions are required to befinished to have a high precision.

At a left end of the second spool member 172, a fitting convex portion172 a having a concentric fitting protruded cylindrical face 172 bprotruded on the axial left side is provided. The fitting protrudedcylindrical face 172 b is formed in dimensions fitted into the fittinghole 171 b and a second coupling hole 172 c is pierced, the secondcoupling hole 172 c is matched with the first coupling hole 171 c in acondition fitted into the fitting hole 171 b and extends in a directionperpendicular to the axis.

In the first spool member 171 and the second spool member 172respectively configured as described above, a coupling pin 173 isinserted into the first and second coupling holes 171 c, 172 c matchedin a condition in which the fitting convex portion 172 a is fitted intothe fitting concave portion 171 a, the first and second spool membersare rockably coupled with the coupling pin 173 in the center to form thevalve spool 70. As a high dimensional precision is required for only theoutside diameter of the guide land 71 in the first spool member 171 andfor only the respective outside diameters of the central land 73 and theleft land 74 in the second spool member 172 respectively by dividing thevalve spool 70 into the first and second spool members 171, 172 asdescribed above, the manufacture of these spool members is facilitatedand the dimensional precision of the outside diameters can be easilyenhanced.

As the coupling pin 173 is relatively moderately inserted into the firstand second coupling holes 171 c, 172 c, a ring 174 is fitted into theholding groove 171 d to prevent the coupling pin 173 from falling out.As a result, the ring 174 is fitted with the ring covering an opening ata peripheral end of the first coupling hole 171 c for closing both endsof the coupling pin 173, and for preventing the coupling pin fromfalling out.

The ring 174 is formed in a coil by bending the wire, which is circularor rectangular in section, in a ring a plurality of times. Therefore,the ring 174 can be easily fitted into the holding groove 171 d byspreading the diameter of the coil. End faces 174 a, 174 b on both sidesof the ring 174 are worked to be flat and as shown in FIG. 19(C), thelateral width of the ring is equal overall. The lateral width is set tobe slightly narrower than the width of the holding groove 171 d and thering 174 is fitted into the holding groove 171 d without rattling.

In this embodiment, the ring 174 is formed by bending the wire in thering a plurality of times to be the coil. However, the ring may be alsoformed by bending a thick wire into a ring only once. However, in thiscase, it is desirable that the ends are overlapped without clearance ina circumferential direction. An inside face of the ring 174 may also beattached to the holding groove 171 d with a loose fit (with clearance).Thus, the valve spool 70 can be easily inserted into the spool hole 6 d.

In the hydrostatic continuously variable transmission CVT configured asdescribed above, a lock-up mechanism 90 is provided, the lock-upmechanism 90 closes the hydraulic closed circuit to be a lock-upcondition when a transmission gear ratio is 1.0, that is, when the inputrevolution speed of the hydraulic pump P and the output revolution speedof the hydraulic motor M are equal. Referring to FIGS. 15 to 17, thelock-up mechanism 90 will be described below. The lock-up mechanism 90is provided with the motor eccentric member 91 slid on the end of themotor casing 30 b as described above. The whole motor eccentric member91 is formed in a ring and the motor-side cam ring 54 is arranged on itsinside face 91 a. A fitting part 91 a is formed at an upper end of themotor eccentric member 91, is fastened to the motor casing 30 b by afitting pin 92, and the motor eccentric member 91 is rockably attachedto the motor casing 30 b with the fitting pin 92 in the center.

To rock the motor eccentric member 91, a lock-up actuator LA is attachedto the motor casing 30 b with the lock-up actuator located on thedownside of the motor eccentric member 91. The lock-up actuator LA isconfigured by a cylinder 96 is fixed to the motor casing 30 b, a piston94 is slidably arranged in a cylinder hole of the cylinder 96, a lid 95that closes the cylinder hole and is attached to the cylinder 96 and aspring 97 that energizes the piston 94 toward the lid 95. The cylinderhole is divided in two by the piston 94, a lock-up hydraulic fluidchamber 96 a and a lock-up release chamber 96 b are formed, and a spring97 is arranged in the lock-up release chamber 96 b. An end of the piston94 is protruded outward from the cylinder 96 and the protruded part 94 ais fastened to a coupling part 91 b formed in a lower part of the motoreccentric member 91 via a coupling pin 93.

In the lock-up mechanism 90 configured as described above, when the oilpressure of the lock-up hydraulic fluid chamber 96 a is released, thepiston 94 is moved on the side of the lid 95 by the energizing force ofthe spring 97 arranged in the lock-up release chamber 96 b. At thistime, as shown in FIG. 16, the coupling part 91 b is touched to an outerend face 96 c of the cylinder 96, in this condition, the center C2 ofthe inside face 91 a of the motor eccentric member 91 is eccentric withthe center C1 of the transmission output shaft 6 and the output rotor(the motor cylinder 32), and the motor eccentric member 91 is located ina normal position.

When the lock-up hydraulic fluid pressure is supplied to the lock-uphydraulic fluid chamber 96 a, the piston 94 is moved to the rightagainst the energizing force by the spring 97 by the fluid pressure asshown in FIG. 17 and the protruded part 94 a is further protruded. Thus,the motor eccentric member 91 is rocked counterclockwise with thefitting pin 95 in the center as shown in FIG. 17 and as shown in FIG.17, a contact face 91 c formed on the side of the motor eccentric member91 is touched to a contact face 98 a of a positioning projection 98integrated with the motor casing 30 a. In this condition, the center C2of the inside face 91 a of the motor eccentric member 91 is overlappedwith the center C1 of the transmission output shaft 6 and the outputrotor (the motor cylinder 32) and the motor eccentric member 91 islocated in a lock-up position.

As is known from the configuration of the hydraulic motor M and theconfiguration of the distributing valve 50 respectively described above,when the motor eccentric member 91 is located in the lock-up position,the center of the motor-side cam ring 54 arranged on the inside face 91a coincides with the rotational center of the motor cylinder 32, even ifthe motor cylinder 32 is rotated, the motor-side spool 55 is notreciprocated, and the supply of high-pressure oil to the motor plunger33 is cut off. At this time, the motor plunger communicates with the oilpassage 56 on the low pressure side. As a result, a reduction in thecompression loss and hydraulic fluid leakage in the motor plunger 33 anda reduction in the mechanical power loss of the bearing and othersoccurs because no high pressure is applied to the motor plunger 33.Further, the reduction in resistance in sliding the pump-side spool 53is enabled, and power transmission is efficiency enhanced.

As known from the above-mentioned description, when lock-up hydraulicfluid pressure is supplied to the lock-up hydraulic fluid chamber 96 ain the lock-up mechanism 90, the motor eccentric member 91 is rocked andis located in the lock-up position to be in the lock-up condition. Thatis, independent of the gear ratio of the hydrostatic continuouslyvariable transmission CVT, if only lock-up hydraulic fluid pressure issupplied to the lock-up hydraulic fluid chamber 96 a, the lock-upcondition can be hydraulically produced. However, as described above, aslockup should be made when the transmission gear ratio is 1.0, lockup isset so that lock-up hydraulic fluid pressure cannot be supplied unlessthe transmission gear ratio is in the vicinity of 1.0. Referring toFIGS. 1, 4 and 20, this configuration will be described below.

Lockup control oil passages 131, 132, 133 for supplying lock-uphydraulic fluid pressure to the lock-up hydraulic fluid chamber 96 a areformed in the transmission housing HSG and the motor casing 30 (30 a, 30b) as shown in the drawings. The lockup control oil passage 131connecting with a lockup control oil pressure supply control valve notshown, is controlled by the valve, and lockup control oil pressure issupplied to the lockup control oil passage. The lockup control oilpassage 133 connects with the lock-up hydraulic fluid chamber 96 a ofthe lock-up mechanism 90. Therefore, basically, an oil pressure supplycontrol by the lockup control oil pressure supply control valve isexecuted and a lock-up operation control can be executed.

However, a branched oil passage 134 branched from the lockup control oilpassage 132 is formed with the branched oil passage open to a concavesupporting cylindrical face 30 c formed on the inside face of the motorcasing 30 and lock-up hydraulic fluid is exhausted in the casing fromthe branched oil passage 134 through an opening 134 a. A convex rockingsupported cylindrical face 35 b that forms the back side of the motorrocking member 35 that rotatably supports the motor swash plate 31 isslid on the supporting cylindrical face 30 c. In a condition wherein anangle of the swash plate is relatively large as shown in FIGS. 1 and 4,the opening 134 a is open. In the meantime, as shown in FIG. 20, whenthe angle of the swash plate is in the vicinity of zero (a swash platesurface is in a direction perpendicular to the axis), the rockingsupported face 35 b covers and closes the opening 134 a of the branchedoil passage 134.

As described above, when the angle of the swash plate is in the vicinityof zero which is substantially zero, that is, when transmission gearration is in the vicinity of 1.0 which is substantially 1.0, the opening134 a of the branched oil passage 134 is closed. Therefore, only in thevicinity of a position of the swash plate angle in which thetransmission gear ratio is 1.0 and lockup is required, the lockupcontrol oil pressure can be supplied to the lock-up hydraulic fluidchamber 96 a via the lockup control oil passages 131 to 133. As theopening 134 a of the branched oil passage 134 is open when an angle ofthe swash plate is except it, that is, when no lockup is required,lockup control oil pressure is exhausted in the casing through thebranched oil passage 134 even if the lockup control oil pressure issupplied to the lockup control oil passage 131 and no lockup control oilpressure acts on the lock-up hydraulic fluid chamber 96 a.

Next, referring to FIGS. 12 to 14 and FIG. 18, the configuration of asystem for supplementing hydraulic fluid in the hydraulic closed circuitwill be described. As shown in FIG. 18, hydraulic fluid is supplementedby the oil pump OP (see FIG. 3) and discharged oil from the oil pump OPdriven by the engine E is supplied to an oil passage 160 axiallyextending in the transmission output shaft 6 via an oil passage in thetransmission housing HSG. The oil passage 160 connects with an oilpassage 161 extending in a radial direction in the transmission outputshaft 6 and opens to the periphery at the end of the oil passage 160.The oil passage 161 further connects with oil passages 162 a, 162 b, 162c axially extending in the output rotor (the motor cylinder 32, thevalve body 51 and the pump cylinder 22), an orifice 164 communicatingwith the outside is formed at the end of the oil passage 162 c, and theinside of the transmission is lubricated by hydraulic fluid that flowsoutside from the orifice 164.

A first check valve 170 a for supplying supplemented oil to the outsidepassage 57 and a first relief valve 175 a for relieving hydraulic fluidwhen oil pressure in the outside passage 57 exceeds a predetermined highpressure are provided in the pump cylinder 22 as shown in FIGS. 12 to14. Further, a second check valve 170 b for supplying supplemental oilto the inside passage 56 and a second relief valve 175 b for relievingthe hydraulic fluid when the oil pressure in the outside passage 57exceeds a predetermined high pressure respectively having the similarconfiguration to the configuration of the above-mentioned valves arealso provided though the two valves are not shown in FIGS. 12 to 14.

An oil passage 163 a that connects the oil passage 162 c and the firstcheck valve 170 a is formed in the pump cylinder 22 as shown in FIGS. 12to 14 and hydraulic fluid supplied from the oil pump OP is supplied tothe outside oil passage 57 via the first check valve 170 a assupplemented oil if necessary (according to leakage from the hydraulicclosed circuit). The plurality of oil passages 162 a, 162 b, 162 c areformed, an oil passage 163 b that connects an oil passage 162 c and asecond check valve 170 b is formed in the pump cylinder 22, andhydraulic fluid supplied from the oil pump OP is supplied to the insideoil passage 56 via the second check valve 170 b as supplemental oil ifnecessary (according to leakage from the hydraulic closed circuit).

Hydraulic fluid relieved from the first relief valve 175 a when oilpressure in the outside passage 57 exceeds a predetermined high pressureset by energizing means is exhausted in a return oil passage 165 aformed in the pump cylinder 22. The return oil passage 165 acommunicates with a ring oil passage 166 formed on the periphery of thetransmission output shaft 6 in a ring, fitted to the pump cylinder 22and is encircled by the pump cylinder. The oil passage 166 communicateswith the oil passage 162 c via the oil passage 163 a and as known,hydraulic fluid relieved from the first relief valve 175 a is exhaustedin an oil passage for supplying supplemented oil supplied from the oilpump OP. Hydraulic fluid relieved from the second relief valve 175 b isalso exhausted in the oil passage 162 c, that is, in a supplemented oilsupply oil passage from the return oil passage 165 b via the ring oilpassage 166 and the oil passage 163 b though the passages are not shown.

As described above, as hydraulic fluid relieved from the first andsecond relief valves 175 a, 175 b is exhausted in the supplemented oilsupply oil passage 162 c trough the return oil passages 165 a, 165 b andrelieved oil is never returned to the hydraulic closed circuit. Thus,the rise in oil temperature in the hydraulic closed circuit can beinhibited. As oil pressure in the supplemented oil supply oil passage162 c is stable, hydraulic fluid in the oil passage on the high pressureside can be efficiently relieved.

As the supplemental oil supply oil passage extends from the transmissionoutput shaft 6 into the output rotor, the first and second relief valves175 a, 175 b and the return oil passages 165 a, 165 b are arranged inthe pump cylinder 22 (the output rotor) and the return oil passages 165a, 165 b connect with the supplemented oil supply oil passage 162 c inthe pump cylinder 22, high-pressure relief structure is compactly housedin the pump cylinder 22 and can be made compact. Thus, the return oilpassages 165 a, 165 b can be reduced. The return oil passages 165 a, 165b connect with the supplemented oil supply oil passages 162 c (and 163a, 163 b) via the ring oil passage 166 circumferentially extending inthe part fitted to the pump cylinder 22 on the outside face of thetransmission output shaft 6 and the oil passages coupling structure inthe part is simple.

The embodiment described above is a continuously variable transmissionadopted for use in a motorcycle. However, the invention is not limitedto being adopted for use in a motorcycle and can be adopted in variouspower transmission mechanism such as a four-wheel vehicle, a vehicleincluding an automobile and a general purpose machine.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. A hydrostatic continuously variable transmission configured by connecting a hydraulic pump and a hydraulic motor via a hydraulic closed circuit to enable variably controlling of the capacity of at least either of the hydraulic pump or the hydraulic motor, shifting the input revolution speed of the hydraulic pump and acquiring the output revolution speed of the hydraulic motor, the hydrostatic continuously variable transmission comprising: a valve spool movably arranged in a spool hole axially extending in a supporting shaft for rotatably supporting the hydraulic pump and the hydraulic motor; a clutch oil passage on the high pressure side connected to an oil passage on a high pressure side forming the hydraulic closed circuit and open to the spool hole; and a clutch oil passage on the low pressure side connected to an oil passage on a low pressure side forming the hydraulic closed circuit and open to the spool hole; wherein the valve spool is provided with a guide part fitted into a guide hole formed in the supporting shaft and guided to be axially moved in the spool hole, and a valve part that is fitted to a part in which the clutch oil passage on the high pressure side and the clutch oil passage on the low pressure side in the spool hole are open for connecting and cutting off the clutch oil passage on the high pressure side and the clutch oil passage on the low pressure side according to the axial movement; and the valve spool is formed by coupling a first spool member provided with a part for forming the guide part, and a second spool member provided with a part for forming the valve part.
 2. The hydrostatic continuously variable transmission according to claim 1, wherein the first spool member and the second spool member coaxially extend and are mutually rockably coupled by a coupling pin extended in a direction perpendicular to the axis.
 3. The hydrostatic continuously variable transmission according to claim 1, wherein two or less peripheral parts of the first spool member for which high dimensional precision is required to fit the peripheral parts to the guide hole in the first spool member are provided on the periphery; and two or less peripheral parts of the second spool member for which high dimensional precision is required to fit the peripheral parts to the spool hole in the second spool member are provided on the periphery.
 4. The hydrostatic continuously variable transmission according to claim 2, wherein two or less peripheral parts of the first spool member for which high dimensional precision is required to fit the peripheral parts to the guide hole in the first spool member are provided on the periphery; and two or less peripheral parts of the second spool member for which high dimensional precision is required to fit the peripheral parts to the spool hole in the second spool member are provided on the periphery.
 5. The hydrostatic continuously variable transmission according to claim 1, wherein when a pressure regulator is moved to the left and the valve spool is moved to the left, an inside branched oil passage and an outside branched oil passage communicate via a right groove in the valve spool and an inside passage and an outside passage communicate.
 6. The hydrostatic continuously variable transmission according to claim 1, wherein when a pressure receptor is moved to the right and the valve spool is moved to the right, an inside branched oil passage and an outside branched oil passage are cut off by a central land of the valve spool and an inside passage and an outside passage are cut off.
 7. The hydrostatic continuously variable transmission according to claim 5, wherein the valve spool is moved to the left when a casing for the pump is still, the inside branched oil passage and the outside branched oil passage communicate and power transmission between the hydraulic pump and the hydraulic motor is cut off to be in a condition wherein a clutch is disengaged.
 8. The hydrostatic continuously variable transmission according to claim 6, wherein when a casing for the pump is driven, the pressure receptor is moved to the right by a centrifugal force depending on the revolutions of the casing for the pump and the valve spool is moved to the right wherein the inside branched oil passage and the outside branched oil passage are gradually cut off by the central land of the valve spool for gradually engaging a clutch.
 9. The hydrostatic continuously variable transmission according to claim 1, wherein the second spool includes a central land, a groove and a left land, the central land includes a first outside diameter, the left land includes a second outside diameter wherein the first outside diameter is less than the second outside diameter.
 10. The hydrostatic continuously variable transmission according to claim 1, wherein the first spool member includes a variable oil chamber forming groove formed on a right side of a guide land with a fitting concave portion being formed at a right end for mating with a fitting convex portion of the second spool member.
 11. A hydrostatic continuously variable transmission comprising: a hydraulic pump operatively connected to a hydraulic motor via a hydraulic closed circuit for enabling variably controlling of the capacity of at least either of the hydraulic pump or the hydraulic motor for shifting the input revolution speed of the hydraulic pump and acquiring the output revolution speed of the hydraulic motor; a valve spool movably arranged in a spool hole axially extending in a supporting shaft for rotatably supporting the hydraulic pump and the hydraulic motor, said valve spool including a first spool member and a second spool member; a clutch oil passage on a high pressure side connected to an oil passage on the high pressure side for forming the hydraulic closed circuit and open to the spool hole; a clutch oil passage on a low pressure side connected to an oil passage on the low pressure side forming the hydraulic closed circuit and open to the spool hole; a guide part formed on the valve spool for fitting into a guide hole formed in the supporting shaft and guided to be axially moved in the spool hole; and a valve part fitted to a part in which the clutch oil passage on the nigh pressure side and the clutch oil passage on the low pressure side in the spool hole are open for connecting and cutting off the clutch oil passage on the high pressure side and the clutch oil passage on the low pressure side according to the axial movement.
 12. The hydrostatic continuously variable transmission according to claim 11, wherein the first spool member and the second spool member coaxially extend and are mutually rockably coupled by a coupling pin extended in a direction perpendicular to the axis.
 13. The hydrostatic continuously variable transmission according to claim 11, wherein two or less peripheral parts of the first spool member for which high dimensional precision is required to fit the peripheral parts to the guide hole in the first spool member are provided on the periphery; and two or less peripheral parts of the second spool member for which high dimensional precision is required to fit the peripheral parts to the spool hole in the second spool member are provided on the periphery.
 14. The hydrostatic continuously variable transmission according to claim 12, wherein two or less peripheral parts of the first spool member for which high dimensional precision is required to fit the peripheral parts to the guide hole in the first spool member are provided on the periphery; and two or less peripheral parts of the second spool member for which high dimensional precision is required to fit the peripheral parts to the spool hole in the second spool member are provided on the periphery.
 15. The hydrostatic continuously variable transmission according to claim 11, wherein when a pressure regulator is moved to the left and the valve spool is moved to the left, an inside branched oil passage and an outside branched oil passage communicate via a right groove in the valve spool and an inside passage and an outside passage communicate.
 16. The hydrostatic continuously variable transmission according to claim 11, wherein when a pressure receptor is moved to the right and the valve spool is moved to the right, an inside branched oil passage and an outside branched oil passage are cut off by a central land of the valve spool and an inside passage and an outside passage are cut off.
 17. The hydrostatic continuously variable transmission according to claim 15, wherein the valve spool is moved to the left when a casing for the pump is still, the inside branched oil passage and the outside branched oil passage communicate and power transmission between the hydraulic pump and the hydraulic motor is cut off to be in a condition wherein a clutch is disengaged.
 18. The hydrostatic continuously variable transmission according to claim 16, wherein when a casing for the pump is driven, the pressure receptor is moved to the right by a centrifugal force depending on the revolutions of the casing for the pump and the valve spool is moved to the right wherein the inside branched oil passage and the outside branched oil passage are gradually cut off by the central land of the valve spool for gradually engaging a clutch.
 19. The hydrostatic continuously variable transmission according to claim 11, wherein the second spool includes a central land, a groove and a left land, the central land includes a first outside diameter, the left land includes a second outside diameter wherein the first outside diameter is less than the second outside diameter.
 20. The hydrostatic continuously variable transmission according to claim 11, wherein the first spool member includes a variable oil chamber forming groove formed on a right side of a guide land with a fitting concave portion being formed at a right end for mating with a fitting convex portion of the second spool member. 